With increasing development of high technology industries, various electronic devices such as power supply apparatuses, air conditioners or projectors become indispensable in our daily lives. During operations of these electronic devices, a great amount of heat is generated. The system stability and the use lives of these electronic devices are dependent on the capability of removing heat.
Take a power supply apparatus for example. The power supply apparatus usually has a fan for quickly removing heat generated during operation of the power supply apparatus. The fan may provide forced airflow for exhausting warm air from the internal portion of the power supply apparatus to the airflow outlet of the power supply apparatus. In addition, a dust-proof element (e.g. an air filter) is usually arranged at the airflow outlet of the electronic device in order to obstruct dust from entering the internal portion of the electronic device and/or exhausting to the environment.
In a case that the dust-proof element has been used for a prolonged period, the degree of dust accumulation becomes more serious and thus the airflow induced by the fan fails to pass through the dust-proof element. Under this circumstance, the heat-removing capability of the power supply apparatus is reduced and the performance of the power supply apparatus is deteriorated. For providing unobstructed airflow, the dust-proof element needs to be periodically cleaned or replaced with a new one.
Conventionally, three mechanisms are used for discriminating whether the dust-proof element needs to be replaced. According to a first mechanism, a notifying signal is generated when the dust-proof element has been used for a certain time period. The first mechanism fails to comply with diverse conditions of using different power supply apparatuses. According to a second mechanism, a notifying signal is generated when the pressure of the airflow passing through the dust-proof element is lower than a threshold value. Since pressure of the airflow is very tiny, it is difficult to accurate measure airflow pressure. In other words, the second mechanism usually erroneously generates the notifying signal. According to a third mechanism, a notifying signal is generated when an intensity of a transmissible light or a reflective light received by an optical receiver is below a threshold value. Since the optical receiver is often contaminated by the dust, the optical receiver will erroneously generate the notifying signal. Under this circumstance, an additional dust cleaner is necessary to clean the optical receiver.
There is a need of providing a wind speed detecting circuit capable of detecting the timing for replacing dust-proof element of electronic device so as to obviate the drawbacks encountered from the prior art.